Process of utilizing the waste products of garnet-works.



J. DAVENPORT.

PROCESS 0F UTILIZING THE WASTEPRODUCTS 0F GARNET WORKS.

APPLICATION FILED IAN- 27.1915- Patented July 25, 1916.

InvenTor. dohn Davenport yfe wd ATTys.

WIInesses. f MM JOHN DAVENPORT, 0F BRIGHTON, MASSACHUSETTS.

PROCESS OF UTILIZING THE WASTE PRODUCTS OF GARNET-WORKS.

Specification of Letters Patent.

Patented July 25, 1916.

Application filed January 27, 1915. Serial No. 4,763.

To all whom it may concern: v

Be it known that I, JOHN DAVENPORT, a citizen of the United States, and resident of Brighton, county of Suffolk, State of Massachusetts, have invented an Improvement in Processes of Utilizing the Waste Products of Garnet-Works, of which the following description, in connection with the accompanying drawing, is a specification, like characters on the drawing representing like parts. i

The object of this invention is primarily to produce from garnet or from garnet ore an abrasive comprising substantially pure alumina; also to produce therefrom a metal alloy adapted for use in steel manufacture tions of the United States and elsewhere I but usually is commingled with a large proportion of quartz and other minerals which make its commercial extraction prohibitive. In a few places, however, notably in New York State and in New Hampshire, quarries exist which comprise a sufliciently high percentage of almandite crystals cemented together by different amounts of quartz, feldspar, etc., to make its extraction a success commercially. Deposits occur also in Spain and from these three sources the majority, and in fact practicallyall, of the garnet which is used as an abrasive is obtained.

In the preparation of the abrasive the garnet ore is crushed in the usual manner, screened, and finally separated. from the quartz by gravity separation, preferably by means of the Sutton, Steele & Steele concentrating tables or by jigs or it may, be

done by means of a magnetic separator.

filled with fine dust, whereas the crystals of the usual silica papers soon become rounded and worn. I I

In the preparation of the abradant as above described a considerable quantity of garnet is reduced to a flour of too great fineness to be useful as an abrasive and this material at the present time is wasted. This garnet flour or dust contains a very high percentage of alumina and silica and the purpose of the process herein described-is to transform this waste product into valuable products which are useful in the arts.

I have found that by heating the garnet flour above described, or in fact the garnet whether in finely pulverized form or other Wise, in a furnace in the presence of a suitable reducing agent, preferably carbon, two useful products may be obtained, first, practically pure aluminum oxid, i. 6., corundum, a well known abradant, and second a ferrosilicon alloy which, as is well known, is useful in the art of steel manufacture.

In the performance of the process herein described any usual form of reducing furnace, preferably an electric furnace may be employed. A convenient form of electric furnace for the purpose is illustrated in section in the accompanying drawing in which the furnace comprises a preferably slightly conical metallic shell 1 which desirably may be made of boiler plate reinforced by hoops or stays 2, suitable rings 3 belng secured adjacent to the upper end of the shell to provide means for transporting the shell and for elevating it in case the furnace is to be dismantled. In preparing the furnace for use this shell is placed upon a base 4 of fire brick. A. carbon conductor 5 adapted to form one of the electrodes of an electric arc may be embedded in the base 4 cable G'leading to a preferably alternating current supply of low voltage and high am- The shell l having been set upon perage. the base l, a lining of fire bricks 7 is built therein and an inner'lining 8 of more re fractory bricks such as dolomite, or magnesite formed therein, a layer 9 of the same material being placed on the bricks forming the bottonr of the furnace. The top of the furnace desirably comprises a hemispherical dome 10 lined with a highly refractory material 11 such as dolomite or magnesite bricks. The dome 10 is provided with suit able eyebolts 12 preferably secured at equal distances from the center thereof to provide means by which the dome may be readily removed from the furnace. The dome is provided adjacent to the center with an aperture l3'or flue to provide for the escape of the gases formed during the action of the furnace. The opposite side of the dome may be provided with a charging aperture 14 and asuitable cover 15 therefor. The other electrode 16 connected to a cable 17 from the supply is slidably mounted centrally of the dome. This electrode is preferably a carbon cylinder supported by a clamp 18 provided with a, rack plate 19 adapted to be engaged by the teeth of a manually or automatically operable gear 20 mounted upon a suitable standard 21 upon the dome.

In the operation of the furnace the electrode 16 is thrust downwardly by rotation of the gear 20 until it contacts with the lower electrode 5. The gear 20 is then rotated in the opposite direction. to cause the electrode 16 to move away from the electrode '5 thereby striking the are. As the charge 22 becomes molten the electrode may be raised gradually to maintain the proper distance between the same and the surface 23 of the molten material.

In the performance of the process with the apparatus above described the furnace is charged with garnet, preferably in the i .form of dust or flour, intimately mixed with a reducing agent, preferably carbon in the form of coke since it is a good conductor of electricity as well as a desirable reducing agent. The carbon should be added to the v garnet in such proportion as'to act as a reducing agent upon only'those compoundswhich are to be reduced out of thegarnet.

Usually eighteen per cent. more or less of' carbon by weight is sufficient to add to the charge but the will depend entirely upon the chemical composition of the garnet ore to be treated. When the furnace is char ed the upper, movable, electrode 16 is st placed in contact w1th the lower electrode 5, the current, preferably an alternating-1 iaeaeea form an arc. The action of the are rapidly reduces the mixture with which the furnace is charged to a molten state since the pure garnet fuses at the relatively low temperature of about 1260" C. The fusing temperature varies with the amount of ferrous impurities contained therein, being lower in proportion to the greater amount of iron contained in the mixture. Additional material may be introduced until a sufiicient amount of molten material is found to be present in the furnace. During the reducing operation an active ebullition occurs, considerable gas being driven ofi. As the reducing operation proceeds the amount of current is gradually increased until the temperature within the furnace. reaches the fusferrosilicon alloy collects in the .form of lumps or nodules at the bottom and throughout the mass which may be sepa rated readily from the alumina after the latter is broken.

When the entire mass is'cooled sufiiciently the furnace may be readily dismantled to permit the mass to be broken up into pieces of suitable size to be crushed in the usual crushers for abradants. This may be accomplished by lifting ofl' first the dome then the ironshell 1, after which the bricks may be removed to expose the solid mass of alumina. This mass may then be broken by sledges or in any suitable mannerand afterward run through the crusher and graded.

. The ferrosilicon may be removed from the crushed material in any convenient manner as by a avityseparator of the Sutton,

Steele & teele type'and may thereafter be packed for sale to the-steel foundries.

I find that by adding silica to the original may be added to the charge to facilitate the fusing and to produce a purer a1umina,but

ordinarily this is not necessary as the garnet is in itself sufliciently rich in silica and iron for the complete success of the process.

. 95 throughout.v I have also discovered that the The process above described has been per formed mainly upon the variety of garnet known as almandite, mined at Wilmot, N. H., an approximate characteristic chemical anlysis of which shows the following:

This analysis is somewhat inaccurate and high on account of the presence of slight im-- purities such as biotite, magnetite, quartz, etc., which are always present to a greater or less extent.

It is to be understood that other reducing agents than carbon, such as calcium or the like may be used in the performance of this process.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is;

1. The method of treating garnet which consists in forming a mixture of pulverized garnet with a reducing agent in sufficient amount to reduce the constituents of the garnet other than alumina and insufficient in amount to reduce the alumina, heating the mixture to the fusing temperature of alumina, maintaining said temperature substantially constant until complete fusion of the mass is attained and until the constituents of the garnet other than alimina have been reduced, then gradually reducing the heat supplied and cooling the molten mass slowly to permit crystallization of the alumina and solidification of the products of reduction.

2. The method of salvaging garnet dust or flour to produce artificial alumina and a ferrosilicon alloy which consists in mixing in an electric furnace thegarnet dust or flour with an amount of pulverized carbon sufficient to reduce the constituents of the garnet other than alumina and insufi'icient to reduce the alumina, electrically heating the mixture to the fusing temperature of alumina, maintaining said temperature substantially constant until the complete fusion of the mass is attained and the ferrosilicon alloy reduced therefrom, gradually reducing the heat supplied by the electric current and finally cooling the mass slowly to permit complete crystallization of the alumina and the formation of the ferrosilicon alloy into lumps or nodules.

3. The method of producing artificial alumina and its ferrosilicon alloy from garnet consisting in mixing the pulverized garnet with carbon sufiicient to reduce the constitucuts of the garnet other than alumina and insufficient to reduce the alumina, adding to the mixture an amount of silica suflicient to insure the complete reduction of the iron content of the mass to a ferrosilicon alloy, heating the mixture to the fusing temperature of alumina and maintaining the same at such temperature until the ebullition ceases and. the reduction of the constituents of the garnet other than alumina is complete, grad ually reducing the heat supplied and finally cooling the molten mass slowly to permit the complete crystallization of the alumina and the solidification into lumps or nodules of the ferrosilicon alloy.

In testimony whereof, I have signed my name to this specification, in the presence of two subscribing witnesses.

JOHN DAVENPORT.

Witnesses CLARENCE E. JONES, THOMAS J. DRUMMoND. 

